Compiler algorithm to implement speculative stores

Abstract

Apparatus for transforming computer software having a branch operation for conditionally bypassing a memory write operation. The apparatus includes computer executable program code stored in one or more computer readable storage media. The computer executable program code includes code for creating a storage location, code for moving the memory write operation above the branch operation, code for selecting a target address for the memory write operation, wherein the storage location is selected if the branch operation bypasses the memory write operation, and code for replacing an address in the memory write operation with the target address.

What is claimed is:  
     
         1 . Apparatus for transforming computer software, said computer software comprising a branch operation for conditionally bypassing a memory write operation, the apparatus comprising: 
 a. one or more computer readable storage media; and    b. computer executable program code stored in the one or more computer readable storage media, the computer executable program code comprising: 
 i. code for creating a storage location;  
 ii. code for moving said memory write operation above said branch operation;  
 iii. code for selecting a target address for said memory write operation, wherein said storage location is selected if said branch operation bypasses said memory write operation; and  
 iv. code for replacing an original address in said memory write operation with said target address.  
   
     
     
         2 . The apparatus of  claim 1 , wherein said code for selecting said target address selects said original address if said branch operation does not bypass said memory write operation.  
     
     
         3 . The apparatus of  claim 1 , wherein said code for creating, moving, selecting and replacing transforms said computer software into low level program code for performing a conditional memory write without a branch operation.  
     
     
         4 . The apparatus of  claim 3 , wherein said low level program code is functionally equivalent to said computer software.  
     
     
         5 . The apparatus of  claim 3 , wherein said low level program code comprises Assembly code.  
     
     
         6 . The apparatus of  claim 3 , wherein said low level program code comprises machine language code.  
     
     
         7 . The apparatus of  claim 1 , wherein said computer executable program code comprises a compiler.  
     
     
         8 . The apparatus of  claim 1 , wherein said computer executable program code comprises an assembler.  
     
     
         9 . The apparatus of  claim 1 , wherein said code for creating said storage location comprises code for creating computer executable instructions which generate one storage location per compilation unit.  
     
     
         10 . The apparatus of  claim 1 , wherein said code for selecting said target address for said memory write operation comprises a select operation.  
     
     
         11 . The apparatus of  claim 1 , wherein said code for selecting said target address for said memory write operation comprises a conditional move operation.  
     
     
         12 . Apparatus for transforming computer software, said computer software comprising a conditional memory write operation, the apparatus comprising: 
 a. one or more computer readable storage media; and    b. computer executable program code stored in the one or more computer readable storage media, the computer executable program code comprising: 
 i. code for creating a local variable;  
 ii. code for selecting either an original address of said conditional memory write operation or an address of said local variable; and  
 iii. code for performing a memory write operation into said selected address.  
   
     
     
         13 . The apparatus of  claim 12 , wherein said computer executable program code comprises a compiler.  
     
     
         14 . The apparatus of  claim 12 , wherein said code for selecting bases said selection on a result of a condition in said conditional memory write operation.  
     
     
         15 . The apparatus of  claim 14 , wherein said code for selecting selects said address of said local variable if said condition is not satisfied.  
     
     
         16 . The apparatus of  claim 12 , wherein said computer software is written in a high level language, and wherein said code for creating, selecting, and performing transforms said computer software into low level program code for performing a speculative store.  
     
     
         17 . The apparatus of  claim 16 , wherein said low level program code is functionally equivalent to said computer software.  
     
     
         18 . The apparatus of  claim 16 , wherein said low level program code contains no control-flow dependencies.  
     
     
         19 . The apparatus of  claim 16 , wherein said low level program code comprises Assembly code.  
     
     
         20 . The apparatus of  claim 16 , wherein said low level program code comprises machine language code.  
     
     
         21 . Apparatus for transforming computer software, comprising: 
 means for reading source code, wherein said source code includes a conditional memory write operation; and    means for generating functionally equivalent code from said source code, wherein said functionally equivalent code contains a data-flow dependency, and wherein said functionally equivalent code is not fully predicated.